Internal combustion engines are known which utilize spark-ignited direct injection (DISI) systems. The fuel injection mechanisms spray a fuel mist directly into each cylinder and inlet air is directed into the cylinder from one or more inlet ports to produce an appropriate air flow and air-fuel mixture in the combustion chamber. The air-fuel mixture is ignited by a spark plug during each cycle of the piston in the cylinder bore. Various piston bowl and combustion chamber configurations have been devised in order to provide appropriate air-fuel mixtures and to direct them toward the spark plug for ignition.
A number of these known systems constitute four-valve systems which contain two inlet valves and two exhaust valves in each cylinder. The two inlet valves introduce air into the combustion chamber and the two exhaust valves remove waste products from the combustion chamber once the combustion is finished. Some smaller bore engines utilize two or three valves. In three valve systems, two inlet valves and one exhaust valve are provided, with the exhaust valve typically being larger than the inlet valves and positioned on one side of the cylinder head while the two inlet valves are positioned on the opposite side.
In efforts to improve ignition under various load conditions and to reduce soot and undesirable emissions, various types of air flows have been induced in the combustion chamber. These include normal tumble flows, reverse tumble flows, and swirl-type flows. The tumble types of air flow produce air flows which circulate around an axis transverse to the axis of the cylinder bore, while the swirl-types of air flow produce air flows with an axis parallel to the axis of the cylinder bore. There also are systems which utilize both tumble and swirl-type air flows separately or in combination at various portions of the combustion cycle.
In order to produce swirl-type air flows, often swirl-type flow activation valves are used in one or more of the inlet ports. Such valve mechanisms contribute additional cost and complexity to the engine system and frequently have difficulties in operation at lower power stages of engine operation.
Three-valve engines reduce the complexity and number of parts of an internal combustion engine, but also often need a swirl control flow activation valve to produce swirl-type air flows. Also, some known three-valve engines require two spark plugs in each cylinder which also adds additional cost and complexity in the operation of the internal combustion engine. In three-valve systems which use a single spark plug, the spark plug is typically positioned off-center from the central axis of the cylinder bore which limits the performance and/or emission characteristics of the engine.
An object of the present invention is to provide an improved three-valve internal combustion engine in which the valve, ports and injector are located and configured in the manner to overcome the above-mentioned shortcomings of previous three-valve internal combustion engines. Another object of the present invention is to provide a more efficient three-valve internal combustion engine which has improved ignition performance and reduced emissions.